Based on the available information, there is some evidence to suggest that long-term use of tigecycline may be associated with an increase in liver enzymes. Tigecycline is an antibiotic medication, sold under the brand name Tygacil, used to treat a variety of bacterial infections [3].

According to a study published in the Journal of Clinical Pharmacology, tigecycline has been associated with elevations in liver enzymes, specifically alanine aminotransferase (ALT) and aspartate aminotransferase (AST) [1]. The study found that 15% of patients who received tigecycline experienced elevations in ALT or AST, compared to 7% of patients in the control group [1]. However, it is important to note that the study did not specifically examine the effects of long-term use of tigecycline on liver enzymes.

Furthermore, the drug's official Medscape page states that tigecycline may cause an increase in liver enzymes, and that liver function should be monitored in patients receiving the medication [2]. However, the page does not provide specific information on the duration or frequency of liver enzyme monitoring, or the potential impact of long-term use on liver enzyme levels.

In summary, based on the available information, there is some evidence to suggest that tigecycline may be associated with an increase in liver enzymes, including ALT and AST. However, the impact of long-term use on liver enzyme levels is not well-studied, and further research is needed to fully understand the potential risks and benefits of long-term tigecycline use.

Sources:
[1] <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1426172/>
[2] <https://reference.medscape.com/drug/tygacil-tigecycline-342527>
[3] <https://www.drugpatentwatch.com/p/tradename/TIGECYCLINE>